In a recent article published in the Electric Power Research Institute’s “EPRI Journal,” the world-renown Palo Alto, Calif.-based research and development organization touted the successful results of a study that it was hired to conduct on behalf of Tri-State’s environmental team to assess the effects of thermal discharge at the G&T’s Nucla Station in southwest Colorado.
During a 1999 permit renewal assessment, the state permit writer noted that although the river was classified as a cold water environment with a temperature standard of approximately 68 degrees, Nucla Station had a warm water effluent limit of 86 degrees. This contradiction in water temperatures triggered an extensive study and potential compliance issues at the plant. Over the next several years, Tri-State’s environmental team conducted temperature and aquatic life studies to gain a better understanding of the river’s ecosystem.
At a 2006 hearing, the various state agencies involved agreed with Tri-State’s assessment that the segment of the river near Nucla Station was a natural temperature habitat transition zone. In addition, the agencies required Tri-State to conduct further studies to determine if the station’s discharge was impacting the aquatic community and what the appropriate temperature habitat classification should be for that section of the river. EPRI assisted with that portion of the study.
In later years, the project team focused on field sampling aquatic biological populations and monitoring river temperatures.
In 2010, Tri-State personnel met with state agencies during a special hearing. Based on the study results, the state agencies agreed that there was no negative impact on the aquatic community from Nucla’s thermal discharge and that the unique ecosystem surrounding the plant merited site-specific standards.
Also, Colorado’s State Water Quality Control Commission determined that the section of the river downstream from the plant should be reclassified as warm. As a result of this study, a new methodology exists to assess thermal discharge effects on a variety of rivers.
In addition to the benefits of successfully having a section of the San Miguel River reclassified, Tri-State avoided the potential cost of installing a chiller to cool the plant’s thermal discharge if higher temperature standards were imposed for the river.
Tri-State personnel involved in the San Miguel River water assessment study were Chantell Johnson, senior environmental planner, Chris Gilbreath, water, waste & EMS compliance manager, Patty Morgan, chemistry/environmental supervisor and Mark Muniz, environmental/water treatment coordinator.